1. Field of the Invention
The present invention relates in general to air conditioning devices, and more particularly to automotive air conditioning devices of a type having a passage structure through which cooled air bypassing a heater core can be blown into a passenger room or blown against a windshield to defrost the same.
2. Background of the Related Art
In order to clarify the task of the present invention, one conventional automotive air conditioning device as shown in FIG. 16 of the accompanying drawings will be outlined, which is disclosed in Japanese Patent First Provisional Publication 57-7714.
In the drawing, denoted by numeral 1 is a dust structure of an air conditioner device, which has at its upstream portion two inlet passages 13 and 14. The passage 13 leads to the outside of the vehicle, while the other passage 14 leads to the passenger compartment. An air intake door 15 is pivotally connected to the duct structure 1, which selectively closes and opens the two passages 13 and 14. Within the duct structure 1, there are installed an electric blower fan 2, an evaporator 3, a heater core 4 and an air-mix door 5. A bypass passage 6 is provided which bypasses the heater core 4. The duct structure 1 is formed with an air outlet structure 7 which has a center air vent 7C, a left air vent 7L and a right air bent 7R. The duct structure 1 further has a foot area air duct 11. The air vents 7C, 7L and 7R of the air outlet structure 7 are directed to a vertically middle portion of the passenger compartment, while the foot area air duct 11 is directed to a lower portion of the compartment. Designated by numeral 8 is a vent door which pivots to control air flowing toward the air outlet structure 7 and designated by numeral 12 is a foot door which pivots to control air flowing toward the foot area air duct 11. As shown, a major passage 9 is defined between the vent door 8 and the air outlet structure 7.
The bypass passage 6 extends from the duct structure 1 just downstream of the evaporator 3 to the major passage 9 just upstream of the air outlet structure 7. The bypass passage 6 has a bypass door 10 pivotally installed therein.
The doors 15, 5, 8, 10 and 12 are moved by respective actuators (not shown) which are controlled by a control unit to which information signals are fed from various sensors including temperature sensors, door angular sensors and a solar radiation quantity sensor. The temperature sensors are mounted on the ceiling and the floor of the vehicle. The temperature difference between the upper and lower portions of the passenger compartment is thus sensed. That is, when, under a Bi-Level blow mode kept selected, a larger temperature difference is sensed, the bypass door 10 is opened. In this case, air which has passed through the air-mix door 5, that is, the mixed air consisting of the air "A" heated by the heater core 4 and the air "B" not heated by the heater core 4 is blown to the foot area of the passenger compartment through the foot area air duct 11, and at the same time, air, that is, the mixed air consisting of the mixed air "A" and "B" which have passed through the air-mix door 5 and the air "C" which has passed through the bypass passage 6 is blown to the vertically middle portion of the passenger compartment through the air outlet structure 7. Because of addition of the air "C" which has passed through the bypass passage 6, the air blown out from the air outlet structure 7 is somewhat cool as compared with the air blown out from the foot area air duct 11, which keeps the heads of the passengers cool and the feet warm. If the temperature difference between the upper and lower portions of the passenger compartment is small, the bypass door 10 is closed.
However, due to its inherent construction, the above-mentioned automotive air conditioning device has failed to give passengers satisfaction in the air conditioning. That is, since the bypass door 10 is constructed to take only the full-open and full-close positions and the control of the bypass door 10 is made by only the temperature difference and the quantity of solar radiation, the temperature control of the air blown into the passenger compartment through the air outlet structure 7 is not finely made in such a manner as to satisfy the passengers.
As is illustrated by a broken line in FIG. 16, the air outlet structure 7 is further provided with defrosting ducts 20 each having openings 22 exposed to the inner surface of a windshield of the vehicle. That is, when the air conditioning device takes a Def/Foot mode, the mixed air "A" and "B" and the air "C" are blown against the inner surface of the windshield through the defrosting duct 20 to defrost the windshield. In order to increase the defrosting ability of the air in the defrosting duct 20, it is desirable to increase the temperature of the air. However, too much warming of the air tends to bring about the undesired head-warm feeling to the passengers. Various tests and examinations have revealed that for obtaining satisfaction in both comfortable air conditioning and effective defrosting, it is preferable to control the temperature of the defrosting air (viz., the air which is led to the defrosting ducts) in such a manner as is depicted by the graphs of FIGS. 17 (a) and 17 (b). However, hitherto, it has been very difficult to control the temperature of the defrosting air in such manner.